Plasma Etching Gas Composition for Selective Silicon Sidewalls
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Solution Overview
Problem
Existing etching methods for insulating films face challenges in achieving high etching selectivity and verticality of side walls, particularly when etching silicon regions with respect to different materials, due to issues with carbon- and fluorine-containing gas and metal halide gas flow rates.
Innovation Solution
An etching method involving a substrate with distinct silicon and non-silicon regions, using a plasma processing apparatus that generates plasma from a gas mixture containing carbon- and fluorine-containing gases, nitrogen-containing gases, and metal halide gases, where the metal halide gas flow rate is lower than the carbon- and fluorine-containing and nitrogen-containing gases, improving etching selectivity and side wall verticality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etching method using plasma generated from mixed gas of WF6 and C4F8 is used, then etching of insulating film can be performed, but etching selectivity and verticality of side walls are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas by introducing a nitrogen-containing gas (such as N2 or NH3) into the plasma generation gas mixture. This parameter change modifies the plasma chemistry to enhance etching selectivity between different insulating films and improves side wall verticality, resolving the contradiction between manufacturing precision and process simplicity.
Solution Approach 2:
The patent uses a composite gas mixture comprising carbon- and fluorine-containing gas, nitrogen-containing gas, and optionally hydrogen-containing gas. This composite approach combines the benefits of different gases: C4F8 provides etching capability, N2/NH3 enhances selectivity and side wall control, and H2 (when added) further improves anisotropy. The synergistic effect achieves high etching selectivity without significantly increasing process complexity.
2Manufacturing precision
If metal halide gas flow rate is increased to improve etching selectivity, then side wall bowing increases
Solution Approach 1:
The patent optimizes the flow rate parameters of the metal halide gas (WF6) to be within a specific range (3-30 sccm) and controls its ratio relative to other gases (C4F8 at 50-200 sccm and N2/NH3 at 100-300 sccm). This parameter optimization achieves high etching selectivity while preventing excessive side wall bowing, resolving the contradiction between selectivity and shape control.
Solution Approach 2:
The patent applies different gas flow rates to different regions of the plasma environment by controlling the metal halide gas flow locally. By limiting WF6 to specific flow rates and ratios, the etching chemistry is locally optimized to achieve high selectivity at the etch front while minimizing side wall reactions that cause bowing, thus maintaining vertical side walls.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances etching selectivity and dimensional uniformity by reducing side wall bowing and tapering, with improved etching selectivity and verticality of the etched recesses, as demonstrated by experiments with varying gas flow rates and gas compositions.
Implementation Method 1
etching the first region by plasma generated from a processing gas containing a carbon- and fluorine-containing gas, a nitrogen-containing gas, and a metal halide gas
Implementation Method 2
plasma generated from a processing gas containing a carbon- and fluorine-containing gas, a nitrogen-containing gas, and a metal halide gas
Data Source
AI summary
In one embodiment, an etching method includes (a) preparing a substrate having a first region including a first material that contains silicon, and a second region including a second material different from the first material, and (b) etching the first region by plasma generated from a processing gas containing a carbon- and fluorine-containing gas, a nitrogen-containing gas, and a metal halide gas. In (b), a flow rate of the metal halide gas is lower than a flow rate of the carbon- and fluorine-containing gas and a flow rate of the nitrogen-containing gas.